U.S. patent application number 13/000033 was filed with the patent office on 2011-12-01 for apparatus for determining abnormal combustion in internal combustion engine.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Hiroki Ito, Kouhei Kiyota, Shingo Korenaga, Shigeki Miyashita, Yusuke Saitou.
Application Number | 20110290004 13/000033 |
Document ID | / |
Family ID | 45003512 |
Filed Date | 2011-12-01 |
United States Patent
Application |
20110290004 |
Kind Code |
A1 |
Korenaga; Shingo ; et
al. |
December 1, 2011 |
APPARATUS FOR DETERMINING ABNORMAL COMBUSTION IN INTERNAL
COMBUSTION ENGINE
Abstract
An object is to provide an abnormal combustion determining
apparatus for an internal combustion engine that can identify a
major factor causing an oil to flow into a cylinder. The abnormal
combustion determining apparatus for the internal combustion engine
that includes a plurality of cylinders detects, for each cylinder,
a cylinder in which abnormal combustion has occurred. The cylinder
in which the abnormal combustion has occurred, and a history of
load applied during an operation are stored in memory. It is
determined whether or not the cylinder in which the abnormal
combustion has occurred and which is stored in memory, is a
specific cylinder. It is determined whether or not load present in
the history stored in memory and used prior to the occurrence of
the abnormal combustion is higher than a threshold value. Based on
a combination of a decision made by the cylinder determining means
and a decision made by the load determining means, a major factor
causing the oil to flow into the cylinder is identified from among
relations established for factors of oil flowing into the cylinder
according to the combination of these decisions made.
Inventors: |
Korenaga; Shingo;
(Susono-shi, JP) ; Miyashita; Shigeki;
(Susono-shi, JP) ; Ito; Hiroki; (Susono-shi,
JP) ; Saitou; Yusuke; (Susono-shi, JP) ;
Kiyota; Kouhei; (Susono-shi, JP) |
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
45003512 |
Appl. No.: |
13/000033 |
Filed: |
May 28, 2010 |
PCT Filed: |
May 28, 2010 |
PCT NO: |
PCT/JP2010/059129 |
371 Date: |
December 20, 2010 |
Current U.S.
Class: |
73/35.01 |
Current CPC
Class: |
F02D 41/0025 20130101;
F01M 13/023 20130101 |
Class at
Publication: |
73/35.01 |
International
Class: |
G01L 23/22 20060101
G01L023/22 |
Claims
1. An apparatus for determining abnormal combustion in an internal
combustion engine having a plurality of cylinders, comprising:
abnormal combustion detecting means for detecting, for each
cylinder, a cylinder in which abnormal combustion has occurred;
abnormality occurring cylinder storage means for storing the
cylinder in which abnormal combustion has occurred; load history
storage means for storing a history of load applied during an
operation; and based on the cylinder stored in the abnormality
occurring cylinder storage means and the history, major factor
identifying means for identifying a major factor causing an oil to
flow into the cylinder from among relations established for factors
of oil flowing into the cylinder according to the abnormal
combustion occurring cylinder and the load.
2. The apparatus for determining the abnormal combustion in the
internal combustion engine according to claim 1, further
comprising: cylinder determining means for determining whether or
not the cylinder stored in the abnormality occurring cylinder
storage means is a specific cylinder; and load determining means
for determining whether or not load present in the history and used
prior to occurrence of the abnormal combustion is higher than a
threshold value, wherein: based on a combination of a decision made
by the cylinder determining means and a decision made by the load
determining means, the major factor identifying means identifies a
major factor causing an oil to flow into the cylinder from among
relations established for factors of oil flowing into the cylinder
according to the combination of the decision made by the cylinder
determining means and the decision made by the load determining
means.
3. The apparatus for determining the abnormal combustion in the
internal combustion engine according to claim 2, wherein: the major
factor identifying means includes oil dropping identifying means
which identifies a major factor causing an oil to flow into the
cylinder as oil dropping when the cylinder stored in the
abnormality occurring cylinder storage means is the specific
cylinder and load present in the history and used prior to
occurrence of the abnormal combustion is higher than the threshold
value.
4. The apparatus for determining the abnormal combustion in the
internal combustion engine according to claim 2, wherein: the major
factor identifying means includes oil rising identifying means
which identifies a major factor causing an oil to flow into the
cylinder as oil rising when the cylinder stored in the abnormality
occurring cylinder storage means is the specific cylinder and load
present in the history and used prior to occurrence of the abnormal
combustion is equal to or less than the threshold value.
5. The apparatus for determining the abnormal combustion in the
internal combustion engine according to claim 2, wherein: the major
factor identifying means includes negative pressure-side blow-by
identifying means which identifies a major factor causing an oil to
flow into the cylinder as an oil contained in a negative
pressure-side blow-by gas when the cylinder stored in the
abnormality occurring cylinder storage means is an unspecific
cylinder and load present in the history and used prior to
occurrence of the abnormal combustion is equal to or less than the
threshold value.
6. The apparatus for determining the abnormal combustion in the
internal combustion engine according to claim 2, wherein: the major
factor identifying means includes atmosphere-side blow-by
identifying means which identifies a major factor causing an oil to
flow into the cylinder as an oil contained in an atmosphere-side
blow-by gas when the cylinder stored in the abnormality occurring
cylinder storage means is an unspecific cylinder and load present
in the history and used prior to occurrence of the abnormal
combustion is higher than the threshold value.
7. An apparatus for determining abnormal combustion in an internal
combustion engine having a plurality of cylinders, comprising: an
abnormal combustion detecting device for detecting, for each
cylinder, a cylinder in which abnormal combustion has occurred; an
abnormality occurring cylinder storage device for storing the
cylinder in which abnormal combustion has occurred; a load history
storage device for storing a history of load applied during an
operation; and based on the cylinder stored in the abnormality
occurring cylinder storage device and the history, a major factor
identifying device for identifying a major factor causing an oil to
flow into the cylinder from among relations established for factors
of oil flowing into the cylinder according to the abnormal
combustion occurring cylinder and the load.
8. The apparatus for determining the abnormal combustion in the
internal combustion engine according to claim 7, further
comprising: a cylinder determining device for determining whether
or not the cylinder stored in the abnormality occurring cylinder
storage device is a specific cylinder; and a load determining
device for determining whether or not load present in the history
and used prior to occurrence of the abnormal combustion is higher
than a threshold value, wherein: based on a combination of a
decision made by the cylinder determining device and a decision
made by the load determining device, the major factor identifying
device identifies a major factor causing an oil to flow into the
cylinder from among relations established for factors of oil
flowing into the cylinder according to the combination of the
decision made by the cylinder determining device and the decision
made by the load determining device.
9. The apparatus for determining the abnormal combustion in the
internal combustion engine according to claim 8, wherein: the major
factor identifying device includes an oil dropping identifying
device which identifies a major factor causing an oil to flow into
the cylinder as oil dropping when the cylinder stored in the
abnormality occurring cylinder storage device is the specific
cylinder and load present in the history and used prior to
occurrence of the abnormal combustion is higher than the threshold
value.
10. The apparatus for determining the abnormal combustion in the
internal combustion engine according to claim 8, wherein: the major
factor identifying device includes an oil rising identifying device
which identifies a major factor causing an oil to flow into the
cylinder as oil rising when the cylinder stored in the abnormality
occurring cylinder storage device is the specific cylinder and load
present in the history and used prior to occurrence of the abnormal
combustion is equal to or less than the threshold value.
11. The apparatus for determining the abnormal combustion in the
internal combustion engine according to claim 8, wherein: the major
factor identifying device includes a negative pressure-side blow-by
identifying device which identifies a major factor causing an oil
to flow into the cylinder as an oil contained in a negative
pressure-side blow-by gas when the cylinder stored in the
abnormality occurring cylinder storage device is an unspecific
cylinder and load present in the history and used prior to
occurrence of the abnormal combustion is equal to or less than the
threshold value.
12. The apparatus for determining the abnormal combustion in the
internal combustion engine according to claim 8, wherein: the major
factor identifying device includes an atmosphere-side blow-by
identifying device which identifies a major factor causing an oil
to flow into the cylinder as an oil contained in an atmosphere-side
blow-by gas when the cylinder stored in the abnormality occurring
cylinder storage device is an unspecific cylinder and load present
in the history and used prior to occurrence of the abnormal
combustion is higher than the threshold value.
Description
TECHNICAL FIELD
[0001] The present invention relates to an apparatus for
determining abnormal combustion in an internal combustion
engine.
BACKGROUND ART
[0002] An internal combustion engine having a knocking sensor is
known, as disclosed, for example, in Patent Document 1. When the
knocking sensor detects knocking, control is performed to retard
ignition timing in order to bring the knocking to an end. This
publication also discloses an abnormal combustion determining
apparatus for an internal combustion engine that determines that
pre-ignition has occurred if the control of retarding the ignition
timing fails to end the knocking and it is found that, on
comparison, an air-fuel ratio after retarding is smaller than that
before the retarding.
PRIOR ART LITERATURE
Patent Document
[0003] Patent Document 1: JP-A-11-247750
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0004] Abnormal combustion may occur when an engine oil
(hereinafter referred to simply as an "oil") flows into a cylinder.
There are a number of factors that cause the oil to flow into the
cylinder. To take appropriate action against the abnormal
combustion, therefore, it is desirable that the factors be
identified. The apparatus of the Patent Document 1 can, however,
only determine that the abnormal combustion has occurred and is not
able to identify the factor causing the oil to flow into the
cylinder.
[0005] The present invention has been made to solve the foregoing
problem and it is an object of the present invention to provide an
abnormal combustion determining apparatus for an internal
combustion engine that can identify a major factor causing an oil
to flow into a cylinder.
Means for Solving the Problem
[0006] First aspect of the present invention is an apparatus for
determining abnormal combustion in an internal combustion engine
having a plurality of cylinders, comprising:
[0007] abnormal combustion detecting means for detecting, for each
cylinder, a cylinder in which abnormal combustion has occurred;
[0008] abnormality occurring cylinder storage means for storing the
cylinder in which abnormal combustion has occurred;
[0009] load history storage means for storing a history of load
applied during an operation; and
[0010] based on the cylinder stored in the abnormality occurring
cylinder storage means and the history, major factor identifying
means for identifying a major factor causing an oil to flow into
the cylinder from among relations established for factors of oil
flowing into the cylinder according to the abnormal combustion
occurring cylinder and the load.
[0011] Second aspect of the present invention is an apparatus for
determining abnormal combustion in the internal combustion engine
according to the first aspect, comprising:
[0012] cylinder determining means for determining whether or not
the cylinder stored in the abnormality occurring cylinder storage
means is a specific cylinder; and
[0013] load determining means for determining whether or not load
present in the history and used prior to occurrence of the abnormal
combustion is thigher than a threshold value,
[0014] wherein: based on a combination of a decision made by the
cylinder determining means and a decision made by the load
determining means, the major factor identifying means identifies a
major factor causing an oil to flow into the cylinder from among
relations established for factors of oil flowing into the cylinder
according to the combination of the decision made by the cylinder
determining means and the decision made by the load determining
means.
[0015] Third aspect of the present invention is an apparatus for
determining abnormal combustion in the internal combustion engine
according to the second aspect,
[0016] wherein: the major factor identifying means includes oil
dropping identifying means which identifies a major factor causing
an oil to flow into the cylinder as oil dropping when the cylinder
stored in the abnormality occurring cylinder storage means is the
specific cylinder and load present in the history and used prior to
occurrence of the abnormal combustion is higher than the threshold
value.
[0017] Fourth aspect of the present invention is an apparatus for
determining abnormal combustion in the internal combustion engine
according to the second or the third aspect,
[0018] wherein: the major factor identifying means includes oil
rising identifying means which identifies a major factor causing an
oil to flow into the cylinder as oil rising when the cylinder
stored in the abnormality occurring cylinder storage means is the
specific cylinder and load present in the history and used prior to
occurrence of the abnormal combustion is equal to or less than the
threshold value.
[0019] Fifth aspect of the present invention is an apparatus for
determining abnormal combustion in the internal combustion engine
according to the second to the forth aspects,
[0020] wherein: the major factor identifying means includes
negative pressure-side blow-by identifying means which identifies a
major factor causing an oil to flow into the cylinder as an oil
contained in a negative pressure-side blow-by gas when the cylinder
stored in the abnormality occurring cylinder storage means is
unspecific cylinders and load present in the history and used prior
to occurrence of the abnormal combustion is equal to or less than
the threshold value.
[0021] Sixth aspect of the present invention is an apparatus for
determining abnormal combustion in the internal combustion engine
according to the second to the fifth aspects,
[0022] wherein: the major factor identifying means includes
atmosphere-side blow-by identifying means which identifies a major
factor causing an oil to flow into the cylinder as an oil contained
in an atmosphere-side blow-by gas when the cylinder stored in the
abnormality occurring cylinder storage means is unspecific
cylinders and load present in the history and used prior to
occurrence of the abnormal combustion is higher than the threshold
value.
Effects of the Invention
[0023] In the first aspect of the present invention, based on the
cylinder stored in the abnormality occurring cylinder storage means
and the history, the major factor causing the oil to flow into the
cylinder can be identified from among the relations established for
the factors of oil flowing into the cylinder according to the
abnormal combustion occurring cylinder and the load.
[0024] In the second aspect of the present invention, based on the
combination of the decision made by the cylinder determining means
and the decision made by the load determining means, the major
factor causing the oil to flow into the cylinder is identified from
among the relations established for the factors of oil flowing into
the cylinder according to the combination of the decision made by
the cylinder determining means and the decision made by the load
determining means. The aspect of the present invention therefore
allows a maximum of four major factors to be identified by
combining the two determining means.
[0025] In the third aspect of the present invention, the major
factor causing the oil to flow into the cylinder can be identified
as the oil dropping when the cylinder stored in the abnormality
occurring cylinder storage means is the specific cylinder and the
load present in the history and used prior to the occurrence of the
abnormal combustion is higher than the threshold value. The aspect
of the present invention therefore allows appropriate action to be
taken against the oil dropping that causes the abnormal combustion
to occur.
[0026] In the fourth aspect of the present invention, the major
factor causing the oil to flow into the cylinder can be identified
as the oil rising when the cylinder stored in the abnormality
occurring cylinder storage means is the specific cylinder and the
load present in the history and used prior to the occurrence of the
abnormal combustion is equal to or less than the threshold value.
The aspect of the present invention therefore allows appropriate
action to be taken against the oil rising that causes the abnormal
combustion to occur.
[0027] In the fifth aspect of the present invention, the major
factor causing the oil to flow into the cylinder can be identified
as the oil contained in the negative pressure-side blow-by gas when
the cylinder stored in the abnormality occurring cylinder storage
means is the unspecific cylinders and the load present in the
history and used prior to the occurrence of the abnormal combustion
is equal to or less than the threshold value. The aspect of the
present invention therefore allows appropriate action to be taken
against the negative pressure-side blow-by that causes the abnormal
combustion to occur.
[0028] In the sixth aspect of the present invention, the major
factor causing the oil to flow into the cylinder can be identified
as the oil contained in the atmosphere-side blow-by gas when the
cylinder stored in the abnormality occurring cylinder storage means
is the unspecific cylinders and the load present in the history and
used prior to the occurrence of the abnormal combustion is higher
than the threshold value. The aspect of the present invention
therefore allows appropriate action to be taken against the
atmosphere-side blow-by that causes the abnormal combustion to
occur.
BRIEF DESCRIPTION OF DRAWING
[0029] FIG. 1 is a schematic diagram for illustrating a system
configuration of a first embodiment of the present invention.
[0030] FIG. 2 is an illustration showing schematically arrangements
of parts around the cylinder 12 shown in FIG. 1.
[0031] FIG. 3 is an enlarged view showing a sliding portion between
the piston 42 and the cylinder 12 shown in FIG. 2.
[0032] FIG. 4 is a map for storing in memory the cylinders in which
the abnormal combustion has occurred, and the number of occurrence
thereof according to a first embodiment of the present
invention.
[0033] FIG. 5 is a map for storing in memory speed, load, and time
during operation according to a first embodiment of the present
invention.
[0034] FIG. 6 is a flow chart showing a routine which the ECU 60
performs for determining the major factor in the abnormal
combustion according to a first embodiment of the present
invention.
[0035] 10 engine [0036] 12 cylinder [0037] 14 intake passage [0038]
20 air flow meter [0039] 22, 22a, 22b turbocharger, compressor,
turbine [0040] 26 throttle valve [0041] 28 intake manifold [0042]
30 surge tank [0043] 32 combustion chamber [0044] 34 intake valve
[0045] 36 exhaust valve [0046] 42 piston [0047] 44 valve stem
[0048] 48 valve stem guide [0049] 50 valve stem oil seal [0050] 52
crankcase [0051] 54 negative pressure-side blow-by gas flow-back
passage [0052] 56 PCV valve [0053] 57 cylinder head cover [0054] 58
atmosphere-side blow-by gas flow-back passage [0055] 60 ECU
(electronic control unit) [0056] 64 cylinder pressure sensor [0057]
66 piston ring [0058] .alpha. threshold value
MODE FOR CARRYING OUT THE INVENTION
[0059] An embodiment of the present invention will now be described
in detail with reference to the accompanying drawings. Like or
corresponding parts are identified by the same reference numerals
in all drawings and will not be redundantly described.
First Embodiment
System Configuration of the First Embodiment
[0060] FIG. 1 is a schematic diagram for illustrating a system
configuration of a first embodiment of the present invention. The
system shown in FIG. 1 includes an internal combustion engine
(hereinafter referred to simply as an engine) 10. The engine 10
includes a plurality of cylinders 12. The present invention is not
concerned with the number and layout of cylinders. An intake
passage 14 and an exhaust passage 16 are connected to each of the
cylinders 12.
[0061] An air cleaner 18 is disposed near an inlet of the intake
passage 14. An air flow meter 20 is disposed downstream of the air
cleaner 18. The air flow meter 20 outputs an intake air amount GA
that corresponds to a flow rate of fresh air drawn into the intake
passage 14.
[0062] A turbocharger 22 is disposed downstream of the air flow
meter 20. The turbocharger 22 includes a compressor 22a and a
turbine 22b. The compressor 22a and the turbine 22b are integrally
connected with each other by a connecting shaft. The compressor 22a
is rotatably driven by exhaust energy of an exhaust gas inputted to
the turbine 22b.
[0063] An intercooler 24 is disposed downstream of the compressor
22a. The intercooler 24 cools fresh air compressed by the
compressor 22a. A throttle valve 26 is disposed downstream of the
intercooler 24.
[0064] An intake manifold 28 is disposed on the intake passage 14
disposed downstream of the throttle valve 26. A surge tank 30 is
disposed upstream of the intake manifold 28. The intake manifold 28
has a downstream portion branching to be connected to each of the
cylinders 12.
[0065] FIG. 2 is an illustration showing schematically arrangements
of parts around the cylinder 12 shown in FIG. 1. The cylinder 12
includes an intake valve 34, an exhaust valve 36, an injector 38,
an ignition plug 40, and a piston 42. The intake valve 34 opens and
closes between the intake passage 14 and a combustion chamber 32.
The exhaust valve 36 opens and closes between the exhaust passage
16 and the combustion chamber 32. Note that the injector 38 shown
in FIG. 2 is structured to inject fuel directly into the cylinder;
however, this is not the only possible arrangement and the injector
38 may be structured to inject fuel into an intake port.
[0066] The intake valve 34 has a valve stem 44 slidably supported
by a valve stem guide 48 disposed in a cylinder head 46. A valve
stem oil seal 50 is disposed between the valve stem 44 and the
valve stem guide 48. The foregoing arrangements apply also to the
side of the exhaust valve 36. The turbine 22b of the turbocharger
22 is disposed on the exhaust passage 16 on a downstream side of
the exhaust valve 36.
[0067] The system of this embodiment further includes a blow-by gas
reduction device (PCV: positive crankcase ventilation). A negative
pressure-side blow-by gas flow-back passage 54 has a first end
connected to a crankcase 52 shown in FIG. 1. An oil separator
chamber 55 and a PCV valve 56 are disposed midway in the negative
pressure-side blow-by gas flow-back passage 54. The negative
pressure-side blow-by gas flow-back passage 54 has a second end
connected to the surge tank 30.
[0068] An atmosphere-side blow-by gas flow-back passage 58 has a
first end connected to a cylinder head cover 57. The
atmosphere-side blow-by gas flow-back passage 58 has a second end
connected to the intake passage 14 on an upstream side of the
compressor 22a.
[0069] The system of this embodiment includes an ECU (electronic
control unit) 60. Various types of sensors, which include the air
flow meter 20 mentioned earlier, a crank angle sensor 62 that
outputs a signal CA corresponding to a rotating angle of a
crankshaft, and a cylinder pressure sensor 64 for detecting a
cylinder pressure, are connected to an input section of the ECU 60.
Various types of actuators, including the throttle valve 26, the
injector 38, and the ignition plug 40 described earlier, are
connected to an output section of the ECU 60. Based on an output
from each of the sensors, the ECU 60 actuates a corresponding
actuator in accordance with a predetermined program to thereby
control an operating state of the engine 10. The ECU 60 can
calculate an engine speed NE from the signal CA from the crank
angle sensor 62.
[0070] Ideal fuel economy or drivability is normally achieved when
the engine 10 is used in accordance with an optimum operation line.
For reasons such as, for example, changes with time, however,
abnormal combustion can occur if an engine oil (hereinafter
referred to simply as an "oil") in amount equal to or more than a
design value flows into the cylinder. Such abnormal combustion
tends to occur at a high rpm range under light load.
[0071] If the high rpm range under light load is used for the
optimum operation line, avoiding the use of the high rpm range
under light load to thereby prevent the abnormal combustion from
occurring degrades acceleration performance, thus aggravating
drivability. Avoiding the use of the optimum operation line
aggravates fuel economy.
[0072] To enable the use of the optimum operation line after
occurrence of the abnormal combustion, it becomes necessary to take
appropriate action to reduce the oil flowing into the cylinder.
However, in order to take the appropriate action, a major factor
causing the oil to flow into the cylinder must first be correctly
identified. If the factor is wrongly identified, wrong action is to
be taken, leading to aggravated drivability or fuel economy.
Characteristic Processes in the First Embodiment
[0073] In the system of this embodiment, therefore, a factor
relating to the oil in the abnormal combustion is to be identified.
Each of first through fourth processes which the system of this
embodiment performs in order to identify the major factor causing
the oil to flow into the cylinder will be described below.
(First Process: Oil Dropping)
[0074] A first process will first be described. The first process
is to identify the abnormal combustion due mainly to oil dropping.
Under heavy load, a boost pressure becomes higher than an internal
pressure of the cylinder head cover 57. Consequently, a gas blows
from the cylinder toward the side of the cylinder head 46. If the
valve stem oil seal 50 has a reduced sealing force due, for
example, to changes with time, an oil flows from the side of the
cylinder head 46 into the cylinder, which is the oil dropping (an
arrow B in FIG. 2). Note that the valve stem oil seal 50 is
disposed independently for each cylinder, so that the abnormal
combustion due to the oil dropping occurs in a specific cylinder,
in which the valve stem oil seal 50 has a reduced sealing
force.
[0075] In the first process, therefore, if heavy load is heavily
used before abnormal combustion occurs and the abnormal combustion
occurs in a specific cylinder, the major factor relating to the oil
in the abnormal combustion is to be identified as oil dropping.
(Second Process: Oil Rising)
[0076] A second process is to identify the abnormal combustion due
mainly to oil rising. FIG. 3 is an enlarged view showing a sliding
portion between the piston 42 and the cylinder 12 shown in FIG. 2.
Normally, an excess oil is scraped off by piston rings 66. When a
tension of the piston rings 66 becomes small due to, for example,
wear, an oil tends to flow into the cylinder. Specifically, the
cylinder pressure during air intake is close to an internal
pressure of the surge tank 30. The cylinder pressure is therefore
negative under light load. In contrast, the internal pressure of
the crankcase 52 is close to the atmospheric pressure.
Consequently, if the tension of the piston rings 66 becomes small,
an oil flows from the side of the crankcase 52 into the cylinder,
which is the oil rising (an arrow C in FIG. 3). Note that the
piston 42 is disposed independently for each cylinder, so that the
abnormal combustion due to the oil rising occurs in a specific
cylinder, in which the tension of the piston rings 66 becomes
small.
[0077] In the second process, therefore, if light load is heavily
used before abnormal combustion occurs and the abnormal combustion
occurs in a specific cylinder, the major factor relating to the oil
in the abnormal combustion is to be identified as oil rising.
(Third Process: Blow-by on a Negative Pressure Side)
[0078] A third process is to identify the abnormal combustion due
mainly to a negative pressure-side blow-by, in which a blow-by gas
flows back through the negative pressure-side blow-by gas flow-back
passage 54. Under light load, the internal pressure of the surge
tank 30 is negative. By contrast, the internal pressure of the
crankcase 52 is close to the atmospheric pressure. Consequently, a
flow-back condition through the negative pressure-side blow-by gas
flow-back passage 54 (crankcase internal pressure-surge tank
pressure>0) holds true. The blow-by gas therefore flows from the
side of the crankcase 52 back to the side of the surge tank 30 as
shown by an arrow D of FIG. 1. Oil contained in the flowing-back
negative pressure-side blow-by gas accumulates in an intake system.
The oil that has accumulated in the intake system thereafter flows
into the cylinder, causing abnormal combustion. Note that the surge
tank 30 is shared among the cylinders, so that the abnormal
combustion due to the negative pressure-side blow-by occurs in
unspecific cylinders.
[0079] In the third process, therefore, if light load is heavily
used before abnormal combustion occurs and the abnormal combustion
occurs in unspecific cylinders, the major factor relating to the
oil in the abnormal combustion is to be identified as an oil
contained in the negative pressure-side blow-by gas.
(Fourth Process: Blow-by on the Atmosphere Side)
[0080] A fourth process is to identify the abnormal combustion due
mainly to an atmosphere-side blow-by, in which a blow-by gas flows
back through the atmosphere-side blow-by gas flow-back passage 58.
The system of this embodiment having the turbocharger 22 has a wide
load range, in which the crankcase 52 internal pressure-the surge
tank 30 internal pressure<0, when the engine is turbocharged.
Under heavy load, therefore, the blow-by gas does not flow back
through the negative pressure-side blow-by gas flow-back passage
54. In this case, a flow-back condition through the atmosphere-side
blow-by gas flow-back passage 58 (crankcase 52 internal
pressure-atmospheric pressure>0) holds true. The blow-by gas
therefore flows from the side of the crankcase 52 back to the side
of the intake passage 14 on the upstream side of the compressor 22a
as shown by an arrow E of FIG. 1. Oil contained in the flowing-back
atmosphere-side blow-by gas accumulates in the intake system. The
oil that has accumulated in the intake system thereafter flows into
the cylinder, causing abnormal combustion. Note that the intake
passage 14 is shared among the cylinders, so that the abnormal
combustion due to the atmosphere-side blow-by occurs in unspecific
cylinders.
[0081] In the fourth process, therefore, if heavy load is heavily
used before abnormal combustion occurs and the abnormal combustion
occurs in unspecific cylinders, the major factor relating to the
oil in the abnormal combustion is to be identified as an oil
contained in the atmosphere-side blow-by gas.
[0082] Specific examples for identifying the major factor relating
to the oil in the abnormal combustion through the first to fourth
processes described above will be described below. FIG. 4 is a map
for storing in memory the cylinders in which the abnormal
combustion has occurred, and the number of occurrence thereof. The
map shown in FIG. 4 stores the cylinders in which the abnormal
combustion has occurred, associated with frequency of occurrence
thereof. FIG. 5 is a map for storing in memory speed, load, and
time during operation. A history of, for example, load is plotted
on FIG. 5 in sequence. The first through fourth processes identify,
from these types of stored data, the major factors causing the oil
to flow into the cylinder.
[0083] If, for example, the abnormal combustion frequently occurs
in a particular cylinder (e.g. a single cylinder) as shown in trips
1 and 7 of FIG. 4, it is known that the factor is either the oil
dropping or the oil rising. Further, from the history of FIG. 5,
the major factor can be identified as the oil dropping (the first
process) if heavy load is frequently used before the abnormal
combustion occurs. On the other hand, if light load is frequently
used before the abnormal combustion occurs, the major factor can be
identified as the oil rising (the second process).
[0084] If the abnormal combustion occurs in unspecific cylinders
(e.g. multiple cylinders) as shown in trips 4 and 5 of FIG. 4, it
is known that the factor is either the negative pressure-side
blow-by or the atmosphere-side blow-by. Further, from the history
of FIG. 5, the major factor can be identified as the negative
pressure-side blow-by (the third process) if light load is
frequently used before the abnormal combustion occurs. On the other
hand, if heavy load is frequently used before the abnormal
combustion occurs, the major factor can be identified as the
atmosphere-side blow-by (the fourth process).
(Abnormal Combustion Major Factor Determining Routine)
[0085] FIG. 6 is a flow chart showing a routine which the ECU 60
performs for determining the major factor in the abnormal
combustion in order to achieve the above-described operations. In
the routine shown in FIG. 6, the ECU 60 stores in memory a trip
history in step 100. For example, the ECU 60 stores in a map
corresponding to that of FIG. 4 the cylinders in which the abnormal
combustion has occurred, associated with the number of occurrence
thereof (or probability). Also stored in a map corresponding to
that of FIG. 5 is a history of the load and the engine speed NE
during the operation. The load can be estimated from, for example,
the engine speed NE and the intake air amount GA. The ECU 60
determines that, if a combustion pressure detected by the cylinder
pressure sensor 64 exceeds a predetermined value, the abnormal
combustion has occurred in that particular cylinder. The operation
of step 100 is repeatedly performed until a predetermined number of
samples are reached.
[0086] After that, in step 110, the ECU 60 determines whether or
not the abnormal combustion has occurred. Specifically, the ECU 60
first acquires, from the trip history stored in step 100, the
number of occurrence of the abnormal combustion (or probability)
for each cylinder. If the number of occurrence of the abnormal
combustion (or probability) is greater than a reference value for
at least one cylinder, it is determined that the abnormal
combustion has occurred. If it is determined that the abnormal
combustion has not occurred, the operation of this routine is
terminated.
[0087] If it is determined in step 110 that the abnormal combustion
has occurred, the ECU 60 next calculates the speed and load before
entry in an abnormal combustion occurrence range (step 120).
Specifically, the ECU 60 calculates, from the trip history stored
in step 100, which specific speed and load are heavily used within
a predetermined period of time before the abnormal combustion
occurs. For example, the ECU 60 calculates an average speed and an
average load in the predetermined period of time before the
abnormal combustion occurs.
[0088] Then in step 130, the ECU 60 determines, from the trip
history stored in step 100, whether or not the abnormal combustion
occurs in a specific cylinder (e.g. a single cylinder). If it is
determined that the abnormal combustion occurs in a specific
cylinder, the ECU 60 subsequently determines, in step 140, whether
or not heavy load is heavily used prior to the occurrence of the
abnormal combustion. Specifically, the ECU 60 determines that heavy
load is heavily used, if the load calculated in step 120 is higher
than a threshold value .alpha. (FIG. 5) and that light load is
heavily used, if the load calculated in step 120 is equal to or
less than the threshold value .alpha. (FIG. 5).
[0089] If it is determined in step 140 that heavy load is heavily
used, the ECU 60 then determines that the major factor causing the
oil to flow into the cylinder is the oil dropping (step 150). The
ECU 60 turns ON a flag indicating that the major factor relating to
the oil in the abnormal combustion is the oil dropping. The
operation of this routine is thereafter terminated.
[0090] If it is determined in step 140, on the other hand, that
light load is heavily used, the ECU 60 then determines that the
major factor causing the oil to flow into the cylinder is the oil
rising (step 160). The ECU 60 turns ON a flag indicating that the
major factor relating to the oil in the abnormal combustion is the
oil rising. The operation of this routine is thereafter
terminated.
[0091] If it is determined in step 130 that the abnormal combustion
occurs in unspecific cylinders (e.g. multiple cylinders), the ECU
60 subsequently determines, in step 170, whether or not heavy load
is heavily used prior to the occurrence of the abnormal combustion.
Specifically, the ECU 60 determines that heavy load is heavily
used, if the load calculated in step 120 is higher than the
threshold value .alpha. (FIG. 5) and that light load is heavily
used, if the load calculated in step 120 is equal to or less than
the threshold value .alpha. (FIG. 5).
[0092] If it is determined in step 170 that heavy load is heavily
used, the ECU 60 then determines that the major factor causing the
oil to flow into the cylinder is the oil contained in the
atmosphere-side blow-by gas (step 180). The ECU 60 turns ON a flag
indicating that the major factor relating to the oil in the
abnormal combustion is the oil contained in the atmosphere-side
blow-by gas. The operation of this routine is thereafter
terminated.
[0093] If it is determined in step 170, on the other hand, that
light load is heavily used, the ECU 60 then determines that the
major factor causing the oil to flow into the cylinder is the oil
contained in the negative pressure-side blow-by gas (step 190). The
ECU 60 turns ON a flag indicating that the major factor relating to
the oil in the abnormal combustion is the oil contained in the
negative pressure-side blow-by gas. The operation of this routine
is thereafter terminated.
[0094] As described heretofore, in accordance with the routine
shown in FIG. 6, the above-described four major factors relating to
the oil in the abnormal combustion can be identified by combining
the process of determining whether the abnormal combustion occurs
in a specific cylinder or unspecific cylinders and the process of
determining whether the load heavily used prior to the occurrence
of the abnormal combustion is higher or lower than the threshold
value .alpha.. In addition, appropriate action can be taken, in
other routines, for the major factors identified in this
routine.
[0095] The system of the first embodiment described above
determines the major factors causing the oil to flow into the
cylinder by combining all of the four processes of from the first
through fourth processes described above. The first through fourth
processes may, nonetheless, be performed singly or in groups of two
or more.
[0096] Additionally, in the system of the first embodiment
described above, the specific cylinder is a single cylinder. This
is, however, not the only possible requirement. The specific
cylinder may be a plurality of cylinders as long as the frequency
of occurrence of the abnormal combustion can be differentiated from
that of any other cylinders than the plurality of cylinders.
[0097] In addition, the system of the first embodiment described
above determines the occurrence of the abnormal combustion based on
the combustion pressure detected by the cylinder pressure sensor
64. This is, however, not the only possible arrangement. For
example, a knocking sensor may be employed instead of the cylinder
pressure sensor and the occurrence of the abnormal combustion may
be determined based on a knocking level detected by the knocking
sensor.
[0098] In the first embodiment described above, the ECU 60 performs
different operations of steps to achieve respective means in the
first to sixth aspects of the present invention as follows.
Specifically, the ECU 60 performs: the operation of step 100 to
achieve the "abnormal combustion detecting means", the "abnormality
occurring cylinder storage means", and the "load history storage
means" in the first aspect of the present invention; the operations
of the steps 110 to 190 to achieve the "major factor identifying
means" in the first aspect of the present invention; the operation
of step 130 to achieve the "cylinder determining means" in the
second aspect of the present invention; the operation of step 140
or step 170 to achieve the "load determining means" in the second
aspect of the present invention; the operation of step 150 to
achieve the "oil dropping identifying means" in the third aspect of
the present invention; the operation of step 160 to achieve the
"oil rising identifying means" in the fourth aspect of the present
invention; the operation of step 190 to achieve the "negative
pressure-side blow-by identifying means" in the fifth aspect of the
present invention; the operation of step 180 to achieve the
"atmosphere-side blow-by identifying means" in the sixth aspect of
the present invention, respectively.
[0099] Furthermore, in the first embodiment, the factors causing
the oil to flow into the cylinder (steps 150, 160, 180, and 190)
determined according to the combination of a cylinder decision made
by the operation of step 130 and a load decision made by the
operations of steps 140 and 170 correspond to the "relation" in the
first and second aspects of the present invention,
respectively.
* * * * *